Process for the manufacture of lubricating oils



March 29, 1938. J. E. SCHULZE PROCESS FOR THE MANUFACTURE OF LUBRICATINGOILS Original Filed May 5, 1932 3.2mm Au ATTORNEY Patented Mar/29,1938 II I 2,112,350

UNITED STATES PATENT OFFICE PROCESS FOR THE MANUFACTURE OF .LUBRICATINGOILS John E. Schulze, Chicago, IlL, assignor, by mesne assignments, toRed River Refining Company, Chicago, 111., a corporation of DelawareOriginal application May 5, 1932, Serial No. 609,508. Divided and thisapplication June 4,

1937, Serial No. 146,496

4 Claims. (Q1. ice-s3) This invention relates generally to'processes forexceeding, and most desirably materially below, the manufacture oflubricating oils; and in par- 25 millimeters of mercury, and attemperatures ticular it relates to the manufacture of lubricatincreasingonly very gradually and uniformly, ing oils by straight overheaddistillation under the lubricating oil constituents being thus pro 5high vacuum, that is, under very low absolute gressively vaporized inthe order of their boiling pressure. However, the invention is notrestricted points and obtained as lubricating oil distillates todistillation of lubricating oils under vacuum, requiring no acidtreatment or filtration to render but it is of greatest present utilityin that field them finished marketable lubricating oils of good P awhich will therefore be more particularly referred color and stability.

to in explaining the principles of the invention. The process of thepresent invention is a part 10 In prior copending application Serial No.of the complete process disclosed in said prior 'ap- 609,508, filed May5, 1932, of which the present plication and is directed moreparticularly to application is a division, this applicant has disnovelfeatures of procedure forming a part of the closed and claimed a novelprocess of manufacsecond stage or phase of said complete process.

1.3 turing high grade lubricating oils directly by An object of thisinvention is to provide a straight overhead distillation under highvacuum, method or process of recharging a distillation the distillatesthus obtained requiring no acid unit or system of the type used inpracticing the treatment or filtration to render them finished secondphase of the aforesaid process whereby high grade lubricating oils ofgood-color and stait is not necessary to shut the unit down, orrebility. The complete process of said prior applilease the vacuum, orclean out the still, before cation comprises generally two principalstages introducing another charge to be run, thus not or phases: onlysaving time, but minimizing heat losses.

In the first stage, there is effected a relatively Qther objects andadvantages of theinvention quick separation of lubricating 011components will become apparent as the description proceeds. from theheavier components of a given crude In order to afford a fullunderstanding of the mineral oil material or charging stock by aconprinciples of the invention, a typical practical tinuous procedurewhich includes rapidly heating embodiment thereof will now be describedin dethe crude material to temperatures sufiiciently tail in connectionwith the accompanying drawhigh to vaporize all the desired lubricatingoil ing which illustratesmore or less diagrammaticomponents underabsolute pressure on the order cally and to some extent in the form of aflow 30 of 50 millimeters of mercury or lower, vaporizing sheet, atypical distillation unit or plant wherein such components at such lowabsolute pressure, the process can be effectively carried out, the andcondensing them under such low pressure principal apparatus or equipmentparts being as one or more lubricating oil distillates substanshown inside elevation, with portions broken tially free of tarry and otherheavier constituents away to disclose certain structural details.

of the crude starting material employed, as well Referring to thedrawing, in utilizing the apas from nearly all of the lighterconstituents paratus system there illustrated in practicing the thereof.The lubricating oil distillates thus obdistilling process of thisinvention, the distillatained by quick separation, while superior insome tion, although essentially batch or discontinuous 40 respects tothose heretofore obtainable by comin character so far as the nature ofthe distilla- 40 parable procedure, are nevertheless charactertionitself is concerned, is nevertheless semi-conized by a small content ofunstabilizing constiiutinuous from the standpoint of plant manipulaents,and they are not the finished, stable lubri-, tion. That is to say,although the lubricating eating oils desired. Said distillates areemployed, oil components are vaporized in the order of their eithersingly or together, as high grade charging respective boiling points,which is characteristic stock in the second stage or phase of the comofbatch distillation, the arrangement of the applete process of said priorapplication. paratus is such that, after running a given charge Inthesecond stage'or phase of the complete down to a residue or bottoms of,say, 5 to 6 per process of said prior application, the quickly sepcent,it is not necessary to shut the unit down,

arated and unfinished lubricating oil distillates or release the vacuum,or clean out the stlll beare subjected, either singly or in mixtures oftwo' fore introducing another charge to be run. This or more, toredistillation by batch or discontinis a point ofgreat practicaladvantage as can uous distillation in which vaporization and subreadilybe seen. sequent condensation of the lubricating oil con- Generallydescribed, the distillation unit, in

5 stituents is effected under absolute pressures not the specific formhere illustrated, comprises a relatively large capacity vaporizer I Iadapted to contain a suitably large volume of the oil to be processed,in a body having an extensive free upper surface to facilitate rapidvaporization. This oil may be one or more of the lubricating oildistillates obtained from the first stage or phase of the completeprocess of said prior application aforesaid. The vaporizer, which inthis instance takes the form of a shell still, is surmounted by a refluxfractionating tower III containing fractionating elements I I2. Theseshould most desirably be of such character that resistance to vapor flowis reduced to the utmost possible minimum consistent with sufficientlyintimate and prolonged contact between the counterflowing Vapor andliquid to ensure adequate fractionation and clean separation ofimpurities from the desiredlubricating oil distillate under theconditions of operation. Liquid reflux is delivered to the top of theseries of annular plates II 2 by distributor I 23 the liquid droppingfrom one plate to the next lower one in filming downwardly over theplate surfaces. By means of curved vanes (not shown) associated withsaid plates, the ascending vapors are given a whirling movement and arealso alternately divided into' three passes or streams and reunited intoa single stream, as they ascend.

In order to reduce to a minimum any possibility of locally overheatingand thus cracking the oil to be run, the vaporizer I I0 is not itselfheated by contact with flame or hot furnace gases, but the oil to beprocessed is heated by continuous passage through a pipe still H3, oilbeing continuously discharged into the vaporizer through line II 4 andwithdrawn therefrom through line I I5 by a centrifugal circulating pumpI I6 and returned through line H! to the pipe still for further heatingto progressively higher temperatures. The oil passes through the tubes01' the pipe still heater at high velocity (e. g. 6 m8 feet per second)and in a stage of extreme turbulence, thereby practically eliminatingany chance of locally overheating and cracking portions of the oil beingprocessed. In order to permit very rapid circulation of a large volumeof oil per minute through the pipe still heater and vaporizer the pipestill may desirably be of what is known as multi-pass construction, fourpasses being indiitial charge of material to cated at H3 for and at H3for the radiant bank, the several passes being connected in parallel bysuitable headers in a known manner. Such an arrange ment, together withthe ample size of the circulating connections H4, H5, H1, and highoperating capacity of pump I I6, permits circulation of the oil throughthe system proximately 650 gallons per minute where, in a typicalinstance, the total initial charge to the system is 21,000 gallons.circulation of the charge through the system, throughout thedistillation, at a per minute rate of about 2 to 4 per cent of thevolume of the inthe unit, is desirable in practice. Since the volume ofthe charge in the unit decreases to a residue of say, 5 to 6 per cent,the circulating rate, in terms of the proof only 2 to 3 the convectionbank of tubes I at the rate of ap- Generally speaking,

circulating pump in operation, the oil is clrculated rapidly through thesystem in closed circuit, as previously described. The rate ofcirculation may be observed by means of a suitable flow meter I22interposed at any convenient point in the circulating lines connectingthe heater and the shell still vaporizer. The pipe still heater, in theprevent example, may be of sufficient capacity (i. e. heating surfacearea) to raise the temperature of the oil in the shell stillapproximately 70 F. per hour, and during-the initial heating up of thecharge, the pipe still heater may be fired at this rate; so that withina period of from 3 to 5 hours, depending on the type of charge being runand other factors, the oil is heated to its initial boiling point. Itmay be stated that prior to running the charging stock into thevaporizer, it is desirable to treat it with approximately 0.2 per centby volume of a neutralizing agent such as caustic soda of about 40 Baumstrength, this neutralizing solution being thoroughly mixed with thecharging stock'.

The system comprising the shell still, the fractionating tower, thereflux condenser I23, and final condenser I24, is held under high vacuumthroughout the entire distillation of the lubricating fractions bypowerful exhausting means which pull all fixed gas and uncondensed vaporout of the system at high velocity through largediameter oiftake I 28.In a typical instance, the absolute pressure in line I25 at the outletof condenser I24, may be 3 millimeters of mercury, while in the vaporspace above the charge in shell still II II it may be 5 to 6millimeters, a loss millimetersin vacuum. Any suitable exhausting meansof suflicient capacity may be used for this purpose, but in practice itis found practical in this instance to use a 3-stage ejector equipment,such as that indicated generally at I26, or a 3-stage reciprocatingWorthington pump especially developed for this purpose. The tail waterfrom operation of the ejec- -ers I23, I24, together with controllingvalves I 29,

I30, whereby the operation of reflux condenser I23 can be regulated andcontrolled to best advantage.

As soon as the temperature of initial vaporization is reached in theshell still, the rate of firing of the pipe still heater is controlledto conform with the rate of distillation desired. In a typical instance,where the initial charge consists of the combined lubricatingdistillates obtained from tower II of the primary system of said priorapplication aforesaid, vaporization of relatively light products beginsat around 350 to 360 F., and the rate of firing is thereafter soregulated as greatly to reduce the rate at which the temperature of theoil increases, especially during the distillation of the lubricating oilfractions proper, which may betaken to begin when the stream coming overshows a viscosity of 50 to 60 seconds Saybolt (at 100 F'.). Thetemperature of the charge at this point is ordinarily about 375 to 400F. From then on until the heaviest lubricating oil fractions have beendistilled over, which usually requires around 12 to 14 hours inaccordance with the present process, the temperature of the charge israised very slowly and at a substantially uniform rate to a finaldistillation temperature of about 560 to 575? F., and not exceeding 600F. as a maximum.

The residue of 5 or 6 per cent, to which the charge.

is run down, is a very heavy high grade lubrieating stock which may beaccumulated and rerun by batch distillation, yielding, directly,overhead distillates as finished high grade lubricating oils of goodcolor and stability, with viscosities as high as seconds Saybolt (at 212F.).

Distillation in the manner just described means a temperature riseapproximating to 200 F. during 12 to 14 hours of, distillation, which isan average rise of less than 0.25 F. per, minute or 15 F. per hour. Itmay be stated that, in practicing the present process, the rate oftemperature increase during distillation should not average more than 05per minute at the most.

The discharge from the pipe still heater to the shell still iscontrolled by a valve 4' in such manner that a slight positive backpressure (e. g. 5 lbs.) is maintained on the oil to minimizevaporization in the tubes of the pipe still heater. After entering theshell still, the line II4 bends down wardly as shown and terminates in adischarge header I30 extending longitudinally of the still and close tothe bottom thereof. This discharge header is provided throughout itslength with numerous small diameter discharge openings I3I whose totalarea may desirably be less than the cross-sectional area of thedischarge header. This restriction of discharge opening area permits thedischarge of the hot oil from the pipe still heater at very highvelocity into the lower part of the shell still in many small jets, thusconstantly maintaining the body of oil in the shell still in highlyturbulent condition and ensuring substantial uniformity of temperaturethroughout said body. The velocity of the oil at the point of dischargethrough the small openings I 3| is on the order of about 30 feet persecond. This provision is of great importance in increasing theefficiency and uniformity of vaporization at the extremely low rate oftemperature increase above referred to, thus further favoring uniformityin composition (narrow cut) of the vapors evolved during a given periodof time, say several minutes, a fact which, in spite of the very lowpressure drop through the fractionator and condenser, as already pointedout, makes for relatively highefiiciency in the subsequent fractionationof said vapors and clean separation from the lubricating distillate ofthe small quantity of relatively volatile malodorous and unstabilizingcontaminants included therewith.

The vapors rising from the oil in the shell still pass through the largediameter vapor offtake I32 into the fractionating tower and through theentrainment separator I33 located in the base thereof. The vapors thenpass upwardly through the system of fractionating plates or trays II2,previously referred to.

The vapor temperature at the top or outlet of reflux condenser I23 iscarefully regulated and controlled throughout the distillation in suchmanner that no condensation of malodorous or unstabilizing products,which are relatively low boiling as compared to the lubricatingconstituents of the distillation vapors, can occur in the refluxcondenser. That is to say, care is taken throughout the distillation toso adjust the water cooling of reflux condenser I23 that the temperatureof the uncondensed vapors and gases leaving the same is always highenough to ensure that, at any given time, said vapors include not onlythose of the aforesaid malodorous and unstabllizing constituents, butalso a small proportion of vapors of the considerably higher boilinglubricating constituents then coming over.

Vapors escaping condensation in reflux condenser I23 pass into condenserI24 where they are cooled to a much lower temperature sufficiently lowto compel most of the residual vapors to condense. This condensate,which is of unpleasant odor and unstable, is led away through line I34and look box I35 to tank I36.

The lubricating oil distillate condensed in the tower III is led away inside stream from collecting plate I31 through line I38 to constant levelseal tank I39. The operation of the fractionating system is so regulatedand controlled that the lubricating distillate leaving the tower at anygiven time is very hot, being practically at its point of initialvaporization. During the greater part of the distillation, thetemperature at which it leaves the column or tower is not more than 50to 60 degrees Fahrenheit below that of the vapors entering the base ofthe column, and only near the commencement of the distillation is itsometimes as much as 100 degrees below that of the vapors entering thecolumn. This aids greatly in preventing absorption of malodorousconstituents from the distillation vapors by the condensate while itremains in the tower; and the possibility of absorption is still furtherminimized by the maintenance of the extremely high vacuum on the hotcondensate even after it leaves the column, thus ensuring withdrawaltherefrom of even minute traces of such volatile contaminants. Thecondensate is withdrawn through line I40 and cooler I4I by pump I42,

.which then pumps it through line I43 to storage.

Line I43 may be provided with sight glass I44 and meter I45, as shown.The lubricating oil cooler I4I may utilize as cooling medium the waterdischarged through line I 21 from the ejector system and condensers atthe top of the tower. The

operation of lubricating oil pump I42 is automatically regulated byfloat control device I46, as indicated.

The lubricating oil distillate going to storage through line I43 is thedesired final product of the process. When the initial charge is one ormore of the unfinished lubricating oil distillates obtained from thefirst stage or phase of the complete process of said prior application,or any similar charging stock, the product obtained is sweet, stable,finished lubricating oil, of excellent color, resulting directly fromstraight overhead distillation and requiring no further refining orpurifying as by acid treatment and/or filtration. Its particularspecifications as toviscosity, boiling range, etc. depend, of course.upon the character of the charging stock used.

The procedure thus far described is typical of the second stage or phaseof the complete process disclosed and claimed in said prior applicationSerial No. 609,508 aforesaid. The process of the present application hasto do with that part of the second stage or phase of the aforesaidprocess whereby the unit may be recharged after running a given chargedown to a desired point, without having to shut the unit down, orrelease the vacuum, or clean out the still, so that the operation of theunit may be semi-continuous in the sense already explained hereinabove.

Referring again to the drawing, a stand-by pump I41, which may desirablybe steam operated, serves in the capacity of a residue pump when. adistillation run or cycle is completed, and also serves to some extentas a charging pump in such manner that the operation of the unit may besemi-continuous, as just mentioned. When a given still charge has beendistilled off until a residue of about 6% remains in the shell still,firing of the pipe still heater is discontinued, centrifugal circulatingpump I I6 is stopped, valve I52 is closed, and circulation of theaforesaid residue is continued at a reduced rate by means of the steamstand-by pump I"; which is arranged in parallel with pump H8 by valvedsuction and discharge connections I41 and l respectively, the valves inthese connections having been opened for the purpose. While thedescribed distillation has been going on, a fresh supply of chargingstock has been prepared for running and has been placed in the chargingtank II8.

When the steam stand-by pump has been operating for some time as justdescribed and the -stream of lubricating oil condensate flowing fromtower III through line I38 has ceased, valve II! in discharge ordelivery line Ill from the pipe still heater is closed, and valves Iand. I49 in residue discharge line I50 are opened, thus causing the hotresidue to be pumped from the system through residue cooler I5I tostorage. Knowing the actual quantity of residue remaining in the systemat the end of the distillation, and knowing the capacity of the steamstand-by pump I41 or observing the rate of flow of the residue asindicated by flow meter I22, an operator can determine the exact timewhen all of the residue has been removed from the shell still. At thistime, the suction valve I52 in line II! leading from the shell stillremaining closed the valve I53 in line I20 leading from the stillcharging tank H8 is opened and the valve in line I41 is closed,

so that the steam stand-by pump then draws fresh charge from the tankthrough branch line I54 in which valve I55 has been opened for thepurpose. The stand-by pump continues to operate until the remainingportion of the residue, which is thus forced through the pipe stillahead of the fresh charge from tank I I8, is entirely removed from thesystem, whereupon valve H4 in the heater discharge line III is opened,and valve I49 in the residue discharge line I50 is closed. The propertime for effecting this operation is readily determined from a knowledgeof the capacity of the tubes in the pipe still heater and the transferlines, and the rate at which the steam stand-by pump is operated. Afurther guide is afforded by noting the temperature drop which suddenlyoccurs at the outlet in the pipe still heater as the last of the hotresidue leaves it. Shortly after the first portion of the fresh chargereaches the shell still, the steam stand-by pump I" is shut down, thevalves in lines III and I" are closed, and the centrifugal circulatingpump is started to complete the charging of the system with freshlubricating oil distillate stock to be run; valve III in the suctionconnection of the pump to the charging tank H8 being opened andremaining open until the charging operation is finished, whereupon it isclosed and valve I52 is opened again. In the meantime firing of thepipe-still has been resumed.

In the particular installation here illustrated, the discharge side ofstand-by pump I41 is also connected by valved line IlI to discharge lineI 50, whereby the pump may draw oil from the shell still through line I"and discharge it directly into line I50, which may be hecessary ordesirable upon occasion. 1 it The,manipulation of the unit to render itsoperation virtually semi-continuous may of course be accomplished inother ways than that described in specific detail hereinabove, suchdescription being given merely by way of concrete example for purposesof explanation. This method of procedure is very advantageous because itrenders operation of the distillation unit materially more economicaland efficient. Since the shell still, fractionating tower, pipe stillheater and all lines connecting the heater with the shell still areinsulated, the whole system which is at a temperature well above 500 F.at the end of the distillation, retains a large amount of heat which isthus conserved and utilized to impart a rise in temperature to the freshcharging stock amounting to 70-80 F. before firing of the pipe stillheater is begun. Also, the interval during which the fresh charge isbeing heated up to initial boiling point for the next distillationisreduced by about one hour as compared to the time required to heat afresh charge up to the same temperature in a cold unit.

Seal tank I38 has a pressure balancing connection I39 to tower III, asshown. Seal tank- I requires a similar pressure balancing connectionunless, as in the illustrated installation, it is located far enoughbelow condenser I! to provide a balancing leg of oil in line Ill.

The temperatures and other detailed operating conditions hereinabovegiven are to be understood merely as indicative of good practice inhandling typical topped crudes such, for example,

'asfUrania (Louisiana) and Columbia (South America) crudes. Obviouslysuch operating conditions will vary to some extent with the type ofcrude charging material, and hence the operating data are to be regardedas given for purposes of illustration and not as rigidly restrictive.

It is very important to rigidly exclude access of air into thedistilling system, since the occurrence of even very slight oxidationmakes it impossible to produce directly, as overhead distillates,finished lubricating oil products of the character here in question. Allseams and joints exposed to temperature changes should be welded, andthe entire system should be made absolutely tight.

By a stable lubricating oil, as the expression is herein employed, ismeant one that does not undergo changes in storage and use which are inthe nature of breakdown or decomposition and which are recognized by theindustry as characterizing inferior lubricating oils. A lubricating oilwhich, upon being heated to 300 F. andbcing held at this temperature for10 minutes, does not darken in'color more than one-half point on thestandard Saybolt color scale, does not acquire a bluish cast in place ofthe desired greenish bloom, and, does not have or develop an unpleasantodor, is a stable oil.

What is claimed is:

1. In a'process of manufacturing lubricating oil, wherein lubricating011 components of a charge of suitable mineral oil are distilled offwhile the charge is being circulated in a closed path orcircuit whichincludes a tube or pipestill heater, a vaporizer and the necessaryconnecting conduits for delivery of oil from the heater to the vaporizerand for return of oil therefrom to the heater, respectively, the methodof auasso vaporizer and to pass it through said heater, .and then, whensubstantially all or most or the residue has been withdrawn from saidvaporizer, introducing a fresh charge of mineral oil into the circuit ata point in said return conduit in order to force any remaining residuethrough said heater and into said delivery conduit for dischargetherefrom, resuming delivery of oil to said vaporizer when substantiallyall the residue has been thus discharged'from the circuit, andcontinuing introduction ofiresh charge until the circuit is fullyre-charged, whereby the circuit may be re-charged in a relatively shorttime while minimizing heat losses and without endangering the heatertubes through overheating.

2. The method as defined in claim 1 which furtherincludes reducing thespeed or oil flow ,in the circuit while the residue is beingdischarged'therefrom and the first portion of the fresh charge is beingintroduced.

3. The method as defined in claim 1 which further includes maintaining alow absolute pressure in the circuit during the distilling andrecharging operations. p

4. The method as defined in claim 1 whichiurther includes maintaining anabsolute pressure of about 6 millimeters of mercury in the vaporizerduring the distilling operation and preventing any substantial increasein pressure in the circuit during the recharging operation.

JOHN E. SCHULZE.

